WHM + cPanel login failed to open session lockfile: FILE=/var/cpanel/sessions/raw==== Disk quota exceeded at /usr/local/cpanel/Cpanel/Session.pm line 238

Error:

failed to open session lockfile: FILE=/var/cpanel/sessions/raw/:vcLgdleh6y8pqVchZOpxJ85a133IKpf7UsU4FrhLW0tFJmVEC7jHZJ90ZtBUKNIZ.lock, Disk quota exceeded at /usr/local/cpanel/Cpanel/Session.pm line 238

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Check the disk size
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# df-Th
you  could see the disc is 100%

Please delete some unwanted files and try login

Fine.